Polymerization of isobutylene



atentedfeb. 11, 1947 2,415,438 POLYMERIZATION F ISGBU'IYEENE Joseph B. McKinley, Pittsburgh, and Donald R.

Stevens, Wilkinsburg, Ea assignors to H151 Research & Development Company, Pittsburgh, Pa, a corporation oil Delaware No Drawing. Application December 20, 194%, Serial No. 570A The present invention relates to the polymerization of isobutylene, and it is particularly concerned with a process for the production of 1,1,3-

trimethylcyclopentane by the thermal polymer-- It is an object achieved by this invention to provide a process for the production of a cyclic dimer of isobutylene. It is more particularly an object achieved by this invention to provide a process for the-production of 1,1,3-trimethylcyclopentane by the thermal polymerization of isobutylene.

We have found that when isobutylene is subjeoted to thermal treatment at temperatures above about 400 C. at pressures of about 300 to 5000 pounds per square inch for a time depending upon the other conditions employed, which may Vary from several minutes to a few hours, polymerization products containing substantial proportions of 1,1,3-trimethylcyclopentane can be produced; and that by subsequently separating the olefins and parafiins from the polymerization products, a substantially, pure 1,1,3-trimethylcyclopentane product can be obtained.

In carrying out the process of this invention,-

we have found that temperatures of about 400 to 600 C. are required for the production of substantial amounts of 1,1,3-trimethylcyclopen- 9 claims. 01. zoo-coo) pass are obtained at pressures above 1100 pounds;-

per square inch, and when operating a batch v process, pressures Within this higher range ar methane, carbon dioxide, flue gas or the like. At any given pressure, the diluent tends to de- Within this range of temperatures, substantial] inch, higher ultimate yields of 1,1,3-trimethylcyclopentane are obtained than at higher pressures. For this reason, pressures within this range recommend themselves for use in continuous processes. On the other hand, best yields per found most advantageous.

We have found it advantageous also to carry out the polymerization of isobutylene in the presence of an inert diluent, such as, nitrogen, steam,

crease the number of contacts of olefin molecules which decreases the rate of reaction, and at the same time, the diluent absorbs part of the heat of the reaction, which is exothermic. The diluent thus constitutes a means of controlling the polymerization, which is particularly important in a continuous system using short contact times, and at the same time efiectively removes considerable of the heat released.

In carrying out the process of our invention, we have found it most advantageous to effect polymerization of isobutylene in a substantially pure state, except for the presence of inert diluents as mentioned above. However, on occasion, mixtures of C4 hydrocarbons such as a C4 cut of cracking gases, may be used. In the latter case, however, some difficulty is encountered in the recovery of pure 1,1,3-trimethylcyclopentane from the products of the reaction. Also, some loss-of isobutylene may be encountered as a result of cross-polymeriaation,

Subsequent to the formation of the polymerization products, as above described, the 1,1,3-trimethylcyclopentane may be isolated therefrom by various means, including particularly reacting out the olefins and unsaturated materials present and fractionation of the products to obtain a fraction boiling within about 0.2 of a degree of 105 C., the boiling point of 1,1,3-trimethylcyolopentane. One method which we have found particularly satisfactory is to first weather the reaction products by heating at a temperature of about 50 C. to remove gases and light hydrocarbons, fractionating the weathered product to isolate a fraction boiling between about and 128 C. For this'purpose, a fractionating column equivalent to about 15 to 16 plates, while maintaining a reflux ratio of 20:1, has proved satisfactory. The fraction boiling be= tween 95 and 128 C. may then be refractiona to separate out a cut boiling between about 100 to 110 C. This cut may then be treated with sulfuric acid for polymerization of the olefins with subsequent separation of the polymers, or with thioglycolic acid and propionic acid followed by washing with caustic soda solution to remove the olefins and other unsaturated products. The olefin-free product thus obtained contains a cyclic dimer and some parammc hydrocarbons. This product may be refractionated to separate out the cyclic dimer from the paraflins. The fraction boiling between about 104.8 and 105.2 C. may be collected. This fraction usually contains at least about 80 per cent of the cyclic dimer hour, at 460-465 C. and 2025 pounds per square product originally contained in the crude polymerization products. This method may be modiv fied by hydrogenating the fraction boiling between 100 and 110 C. to effect saturation of the olefins and other unsaturates present, and subsequently fractionating the hydrogenated products to separate out the 1,1,3-trimethylcyclopentane. T

Following are illustrative examples which typify presently-preferred embodiments oi the invention.

Examine 1 321 grams of isobutylene were transferred into a high-pressure bomb having a capacity of 1715 cc. Heat was applied until a temperature-of 400 C. was reached, this temperature being maintained for one hour. The pressure rose to 2050 pounds per square inch and fell to 1080 pounds per square inch at the endof the hour.

The bomb was then cooled quickly by applying an air blast.

The total gas-condensed was found to weigh 128.0 grams. It analyzed as follows:

[sobutene C UHSMUX'SCQS... C unsaturstes The weathered liquid product (243.2 cc.185 grams) was fractionated through a column equivalent to 16 plates, while maintaining a. :1 reflux ratio. The fraction collected between 95 and 128 C. was taken as the crude dimer fraction. Analysis showed that this crude dimer fraction contained 65.0 parts by weight of the cyclic dimer, 1;,1,3-trimethylcyclopentane.

Similar runs were carried out at 430 C. and 2025 pounds per square inch for a period oi 1 2 hours. Results are tabulated in the following table:

Table I Run No l 2 3 4 Temperature, C 400 430 460-405 365-370 Time, hours 1 l l. 1 2 Pressure, lbs/sq. inJ. 2, 050 2, 025 2, 025 2, 120 Yieldz Total liquid product,

person 3 57.7 72.9 51.7 34.2 Crude dimer 015-428"),

per can 23.6 33.4 21.7 11.0 Cyclic dimer, per cent 15.3 23.4 l6. 1 6.0 Coke, per cent 0 Trace 4. 7 0 Liquid product:

Crude dimer, per cent- 40. 9 45. 9 42. 0 32. 2 Cyclic dimer, per cent. 20.6 32. 1 31. 0 17.4 Crude dimer (Qt-128):

Sp. gr. 20l4 G 0. 7389 0.7420 0. 7532 0. 7356 Reflective index, un t... 1. 4101 1. 4107 1. 4102 1. 4100 Bromine number 88.0 30.0 35. 0 56. 0 11s, per cent 8. 0 0.0 2.0 7.0 Unsstursteds, per cent... 27.0 21.0 24.0 39. 0 Cyclic dimer, per cent. 85. 0 70. 0 74. 0 54. 0

The liquid 4 action; as t e run inch for a period of 1 hour, and at 365-370 C. and 2120 pounds per square inch for a period of Reaction pressures shown in this and following tabulations are maximum ressures attained in the bomb at the start the reroceoded, the lpressure always decreased.

l Yields shown this and ioi owing tabulations are based on isobut lene charged, unless otherwise indicated.

U ess otherwise indicated, percentages in this and following tabulations are percentages by weight.

EXAMPLE H Runs similar to those of Example I were also carried out at 400 C. and 540 pounds per square inch, 400 C. and 1280 pounds per square inch, and 400 C. and 5350 pounds per square inch, the run in each case being for a period of 1 hour.

Results are tabulated in the following table:

It will be observed from these results that at a pressure of 540 pounds per square inch the total liquid product obtained was less than that obtained at higher pressure, but that the per- 4 centage of cyclic dimer present in the total liquid product was substantially higher than was obtained at higher pressure. These results indicate that under some conditions, particularly in continuous operation, lower pressures may be more advantageous.

EXAMPLE m The following table sets forth the results of two runs made under similar conditions of temperature and pressure but at different times:

Total liquid product, per cent 45.4 77.5 Crude dimer (-128" (2.), per

cent 18.7 29.9

Cyclic dimer, per cent; 11.2 20.6

Table III.-Continued Liquid product:

Crude dimer 95-128 0.), per

cent 41.3 38.6 Cyclic dimer, per cent 24.8 26.6.

Per cent cyclic dimer in crude dimer 60.0 69.0

EXAMPLE IV A run similar to those of Example I was carried out in thepresence of added nitrogen, with the following conditions and results:

l The partial pressure of the isobutylene is about 1750 pounds per square inch.

2 Volume of bomb 1715 cc..

In addition to nitrogen, other diluents such as steam or methane may be employed. At a given pressure, the diluent tends todecrease the number of collisions of olefin molecules, which decreases the rate of reaction and, at the same time, absorbs part of the .heat of the exothermic reaction. The diluent thus constitutes a means of controlling the polymerization, which is particularly important in a continuous system using short contact times during which the rate of polymerization is'very fast and considerable heat is released.

EXAMPLE V Comparison of the following runs carried out, respectively, at 510-520 C. for 4 minutes and at 425 C. for 57.5 minutes, indicate the essential equivalence of time and temperature inthe process according to the present invention:

Time, minutes 4 57.5 Temperature, C 510-520 425 Pressure, lbs/sq. in 500 500 Yield:

Total liquid product, per cent 28.9 28.0 Crude dimer (95-128 0.), per

cent 13.9 17.2. Cyclic dimer, per cent 6.8 8.6 Liquid product: Crude dimer, per cent 48.2 61.4 Cyclic dimer, per cent 23.5 30.7

In these two runs, which were carried out in a continuous apparatus, the pressures indicated were the operating pressures throughout the runs EXAMPLE VI Isolation of cyclic dimer from liquid product 384 g. of weathered liquid product, obtained according to Example I and, according to anal-' yses, containing 102.1 g. of the cyclic dimer, 1,1,3-trimethylcyclopentane, were charged into a still equipped with a l5-plate column and were fractionated to give 138.8 g. of product boiling between 100 and 110 C. at 760 mm.

This fraction was then washed three times with 83.0% sulfuric acid to effect solution or polymerization, or both, of the olefins present. An individual washing was accomplished by shaking the fraction with a two volume portion of the acid in a separator for 10 minutes and then allowing one-half hour for the phases to separat before drawing off the acid layer. The p d from the acid treatment amounted to 120.9 go after alkali and water washing and drying with calcium chloride. The product from the acid treatment was then distilled through an efficient fractionation column (-plate) using a reflux ratio of 50:1 to obtain a 91.6 g. fraction boiling between 104.7 and 105.3 C. at 760 mm. Most of this product distilled at l05.0, C. and it consisted substantially of the cyclic dimer. The properties of this product are shown below in comparison with the corresponding properties of 1, 1,3-trimethylcyclopentane:

Another product obtained according to the method of Example IV was fractionated through a 45-plate column to obtain cc. of material boiling at to 105.1 C. This fraction was filtered through silica gel and refractionated through a, 62-plate column. The properties of the heart out are shown below in comparison with the theoretical properties of 1,1,3-trimethylcyclopentane and with the .properties of the latter as synthesized from 1-chloro-1,3-dimethylcyclopentane according to the process described and claimed in copending application, Serial No. 570,474, filed on even date herewith and entitled Synthesis of 1,1,3-trimethylcyclopentane.

According to the said copending application, purified 1-chloro-1,3-dimethylcyclopentane is converted into crude 1,1,3-trimethylcyclopentane by treatment with zinc dimethyl, using xylene as solvent, and also by treatment with methyl magnesium iodide in dibutyl ether. The crude reaction products, with added xylene, from both preparations are individually fractionated through a 62-plate column. Heart cuts boiling at about 105 C. are taken and purified by filtering through silica gel to free them from traces of unsaturates and added xylene.

Comparison of 1.1,3-trimethylcylopentane with the cyclic dimer of isobutylene Cyclic Product Zinc dimer of dimcthyl Thieotlet of isobu- Grignard reaction t tylene reaction product pro uc Boiling pt., 760 mm., C. 105.0 105. Sr). gr. at 20l4 C. 0.7480 0.7481 Refractive index, 7113 1. 4108 l. 4109 Molecular weight 113 113 Viscosity at 20 0.:

Gentistoke 0. 828 0.827 .Centlpoise. 0.619 0.619 Aniline point, C. 59. 8 59. 7 Carbon, per cent 85.82 85. 81 Hydrogen, per cent 14.51 14.49 Weight carbon-hydrogen ratio 5. 91:1 5. 92:1 Molecular reiraction 37. 22 37. 22

The agreement between the properties of 1,1,3- trimethylcyclopentane, theoretical and produced according to the aforedescribed syntheses, and those of the cyclic dimer shows that the latter is 1,1,3-trimethylcyclopentane. The amount of the cyclic dimer isolated according to the procedure or the present example was about 90 per cent of that present in the crude product.

Fractionation through an emcient column would be an alternative procedure for recovering the 1,1,3-trimethylcyclopentane. It is also possible to fractionate out a narrow boiling cut (1045-1055 C.) from a crude reaction product.

' The narrow boiling cut may be hydrogenated to convert the olefins present into saturated bodies having difierent boiling points than the unsatu-' rates from whichthey may be derived. The hydrogenated product may then be fractionated through an efiicient column to eflect separation oi 1,1,3-trimethylcyclopentane.

1,1,3-trimethylcyclopentane from the reaction products.

2. A continuous method for the production of 1,1,3-trimethylcyclopentane which comprises subjecting isobutylene to a temperature within the range of 400 to 600 C. at a pressure within the range of about400 to 900.pounds per square inch for a time suflicient to eifect substantial cyclic polymerization of the isobutylene, and separating 1,1,3-trimethylcyclopentane from the reaction products.

3. A discontinuous method for the production oi. 1,1,3-trimethylcyclopentane which comprises subjecting isobutylene to a temperature within the range of 400 to 600 C. at a pressure above about 1100 pounds per square inch for a time suflicient to effect substantial cyclic polymerization of the isobutylene, and separating 1,1,3-trimethylcyclopentane from the reaction products.

'4. A method for the production of 1,-1.3-trimethylcyclopentane which comprises subjecting a (a w for a time sufiicient to efiect substantial cyclic polymerization of the isobutylene, and separating 1,1,3-trimethylcyclopentane from the reaction products.

7. A method for the production of 1,1,3-t-rimethylcyclopentane which comprises subjecting isobutylene to a temperature within the range of 400 to 600 C. at a pressure within the range or about 300 to 5000 pounds per square inch for a time within the range of about 3 minutes to 4 hours, and separating the 1,1,3-trimethyicyclopentane from the reaction products by reacting out the unsaturated constituents of the reaction products and fractionally distilling the residue to recover a fraction boiling between about 104.7 and 105.3 C.

8. A method for the production of 1,1,3-trimethylcyclopentane which comprises subjecting isobutylene to a temperature within the range of 400 to 600 C. at a, pressure within the range oi. about 300 to 5000 pounds per square inch for a time within the range of about 3 minutes to 4 hours, and separating the 1,1,3-trimethylcyelopentane from the reaction products byfractionatisobutylene to-a'temperature within the range of 400 to 600 C. at a pressure within the range of about 300 to 5000 pounds per square inch in the presence of an inert diluent, for a time sufficient to efiectsubstantial cyclic polymerization of the isobutylene, and separating 1,1,3-trimethylcyclcpentane from the reaction products.

5. A method for the production of 1,1,3-trimethylcyclopentane which comprises subjecting Numberisobutylene to a temperature within the range of isobutylene to a temperature within the range of about 425 to 525 C. at a pressurewithin the range of about 300 to 5000 pounds per square inch ing the reaction products to recover a. fraction boiling between and C., reacting out the unsaturated constituents and fractionally distilling the residue to recover 'a fraction boiling between 100 and 110 C., washing said fraction with sulfuric acid to remove unsaturated products, neutralizing and drying the washed reaction prodnets and fractionally distilling to recover a prod uct boiling between about 104.7 and 105.3 C.

JOSEPH B. MCKINLEY. DONALD R. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 1,981,819 Wiezevich. Nov. 20, 1934 1,987,007 Frey Jan. 8, 1935 1,991,354 Plummer Feb. 12, 1935 2,111,831 Batchelder Mar. 22, 1938 2,314,040 Frey Mar. 16, 1943 OTHER REFERENCES Ipatiefi "Cat. Reactions at High Press. and Temps; 1936; pages 572-578. (Copy in Div. 31.) Zelinskii et al. article in Jour. Russ. Phys. Soc;

vol. 45, pages 831-842; Ber. vol. 46, pages 1466- 1474; C. A. vol. 7, page 3600 (1913).

Dunstan, Science of Petroleum; vol. 3; 1938; page 2027. (Copy in Div. 31.) 

